This invention relates to a method of manufacturing an electron-beam source having a plurality of electron-emitting devices and an image forming apparatus using the electron-beam source and an activation processing method.
Conventionally, two type of electron-beam sources, namely thermionic cathodes and cold cathode electron-beam sources, are known as electron-emitting devices. Examples of cold cathode electron-beam sources are electron-emitting devices of field emission type (hereinafter abbreviated to xe2x80x9cFExe2x80x9d), metal/insulator/metal type (hereinafter abbreviated to xe2x80x9cMIMxe2x80x9d) and surface-conduction emission type (hereinafter abbreviated to xe2x80x9cSCExe2x80x9d).
Known examples of the FE type electron-emitting devices are described by W. P. Dyke and W. W. Dolan, xe2x80x9cField Emissionxe2x80x9d, Advance in Electron Physics, 8, 89 (1956) and by C. A. Spindt, xe2x80x9cPhysical properties of thin-film field emission cathodes with molybdenum conesxe2x80x9d, J. Appl. Phys., 47,5248 (1976).
A known example of the MIM type electron-emitting devices is described by C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devicesxe2x80x9d, J. Appl. Phys., 32,646 (1961).
A known example of the SCE type electron-emitting devices is described by, e.g., M. I. Elinson, xe2x80x9cRadio Eng. Electron Phys., 10, 1290 (1965) and other examples to be described later.
The SCE type electron-emitting device utilizes a phenomenon where an electron emission is produced in a small-area thin film, which has been formed on a substrate, by passing a current parallel to the film surface. As the SCE type electron-emitting device, electron-emitting devices using an Au thin film, an In2O3/SnO2 thin film, a carbon thin film and the like are reported by G. Dittmer, xe2x80x9cThin solid Filmsxe2x80x9d, 9,317 (1972), M. Hartwell and C. G. Fonstad, xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, 519 (1975), Hisashi Araki et al., xe2x80x9cVacuumxe2x80x9d, vol. 26, No. 1, p. 22 (1983), in addition to an SnO2 thin film according to Elinson mentioned above.
FIG. 34 is a plan view of the SCE type electron-emitting device according to Hartwell and Fonstad described above, as a typical example of device construction of these SCE type electron-emitting devices. In FIG. 34, reference numeral 3001 denotes a substrate; 3004, a conductive thin film of a metal oxide formed by spattering, having a H-shaped pattern. An electron emission portion 3005 is formed by an electrification process referred to as xe2x80x9cformingxe2x80x9d to be described later. In FIG. 34, the interval L is set to 0.5-1 mm, and the width W is set to 0.1 mm. Note that the electron emission portion 3005 is shown at approximately the center of the conductive thin film 3004, with a rectangular shape. For the convenience of illustration, however, this does not exactly show the position and shape of the actual electron emission portion 3005.
In these conventional SCE type electron-emitting devices by M. Hartwell and the others, typically the electron emission portion 3005 is formed by performing electrification processing (referred to as xe2x80x9cforming processingxe2x80x9d) on the conductive thin film 3004 before electron emission. According to the forming process, electrification is made by applying a constant direct current where voltage increases at a very slow rate of, e.g., 1V/min., to both ends of the conductive film 3004, so as to partially destroy or deform the conductive film 3004, thus form the electron emission portion 3005 with electrically high resistance. Note that the destroyed or deformed parts of the conductive thin film 3004 have a fissure. Upon application of appropriate voltage to the conductive thin film after the forming processing, electron emission is made near the fissures.
The above-described SCE type emitting devices are advantageous since they have a simple structure and they can be easily manufactured. Therefore many devices can be formed on a wide area. Then, as disclosed in Japanese Patent Application Laid-Open No. 64-31332 by the present applicant, a method for arranging and driving a lot of devices has been studied.
Regarding application of SCE type electron-emitting devices to, e.g., image forming apparatuses such as an image display apparatus and an image recording apparatus, and electron-beam sources have been studied.
Especially, as application to image display apparatuses, as shown in the U.S. Pat. No. 5,066,833 by the present applicant, an image display apparatus using the combination of a SCE type electron-emitting device and a fluorescent material which emits light upon reception of electronic beam has been studied. This type of image display apparatus is expected to have better characteristics than other conventional image display apparatuses. For example, in comparison with recently focused liquid crystal display apparatuses, the above display apparatus is superior in that it does not require a backlight since it is a self light-emitting type and that it has a wide view angle.
The present inventors have examined various SCE type electron-emitting devices having various structures, of various materials, according to various manufacturing methods. Further, the inventors have studied an electron-beam source where a large number of SCE type electron-emitting devices are arranged, and an image display apparatus utilizing the electron-beam source.
The inventors have also examined an electron-beam source by an electrical wiring method as shown in FIG. 31. The electron-beam source is constructed by arranging SCE type electron-emitting devices two-dimensionally, into a matrix.
In FIG. 31, numeral 4001 denotes SCE type electron-emitting devices; 4002, row-direction wiring; and 4003, column-direction wiring. The line-and column-direction wiring 4002 and 4003 actually have limited electric resistances. However, in FIG. 31, the electric resistances are indicated as wiring resistances 4004 and 4005. The wiring in FIG. 31 is referred to as xe2x80x9csimple matrix wiringxe2x80x9d.
Note that in FIG. 31, the electron-beam source is shown with a 6xc3x976 matrix for the convenience of illustration. However, the matrix size is not limited to this arrangement but may be any size as far as the matrix have devices of a number for a desired image display in case of, e.g., an electron-beam source for an image display apparatus.
In the electron-beam source having matrix-wired surface-conduction electron-emitting devices as shown in FIG. 31, to output a desired electron beam, appropriate electric signals are applied to the row- and column-direction wirings 4002 and 4003. For example, to drive SCE type electron-emitting devices in an arbitrary one line in the matrix, a selection voltage Vs is applied to the row-direction wiring 4002 at the line to be selected, at the same time, a non-selection voltage Vns is applied to the row-direction wiring 4002 at the lines not to be selected. In synchronization with this operation, a drive voltage Ve for outputting an electron beam is applied to the column-direction wiring 4003. According to this method, if voltage down by the wiring resistances 4004 and 4005 are ignored, the SCE type electron-emitting devices of the selected line receive a Vexe2x88x92Vs voltage, while the SCE type electron-emitting devices of the non-selected lines receive a Vexe2x88x92Vns voltage. If the voltages Ve, Vs and Vns are respectively set to an appropriate voltage value, an electron beam having a desired intensity is emitted only from the surface-conduction electron-emitting devices of the selected line. Further, if drive voltages Ve""s of different values are applied to respective wire of the column-direction wiring 4003, electron beams of different intensities are emitted from the respective devices of the selected line. As the surface-conduction electron-emitting devices have a high response speed, an electron-beam emission period can be varied by changing an application period of applying the drive voltage Ve.
Thus, the electron-beam source having a simple-matrix wired SCE type electron-emitting devices provides various possibilities of application. For example, it can be used as an electron-beam source for an image display apparatus if appropriate application of an electric signal is made in accordance with image information.
However, the above electron-beam source actually has a problem as follows.
That is, regarding surface-conduction electron-emitting devices used in an image forming apparatus and the like, further increase of emission current and improvement of emission efficiency are desired. Note that xe2x80x9cefficiencyxe2x80x9d means a current ratio of current emitted in vacuum (hereinafter referred to as xe2x80x9celectron emission current Iexe2x80x9d) with respect to current that flows when a voltage is applied to device electrode of each of surface-conduction electron-emitting devices (hereinafter referred to as xe2x80x9cdevice current Ifxe2x80x9d).
Accordingly, an object of the present invention is to provide a processing method for increasing emission current of an electron-beam source having a plurality of electron-emitting devices.
Another object of the present invention is to provide a processing method for performing the above processing in a short period.
Another object of the present invention is to provide a processing method for uniforming emission current characteristics among a plurality of electron-emitting devices.
According to the present invention, the above objects are attined by providing an electron-beam source manufacturing method comprising an activation step of generating activation material at a plurality of electron-emitting devices, by dividing the plurality of electron-emitting devices into plural groups and sequentially applying voltages to each group.
Further, the present invention provides a method for manufacturing an image forming apparatus which comprises an image forming unit for forming an image by irradiation of electron beams from an electron-beam source having a plurality of electron-emitting devices, wherein the electron-beam source is manufactured in accordance with the above method.
Further, the present invention provides an electron-beam source activation method for activating an electron-beam source having a plurality of electron-emitting devices comprising an activation step of generating activation material at a plurality of electron-emitting devices, by dividing the plurality of electron-emitting devices into plural groups and sequentially applying voltages to each group.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.